1. Field of the Invention
The present invention relates to a battery of a mobile communication terminal and, more particularly, to a structure and operation method of a battery pack adapted for minimizing a memory effect.
2. Description of the Background Art
In general, various types of electric/electronic devices are driven by electrical power, and fixed large-scale electric/electronic devices having a large volume or weight are supplied with power converted by a voltage booster or voltage reducer.
Meanwhile, in case of portable electric/electronic devices such as notebook computers or mobile phones, they are generally supplied with power from a battery because of their incapability of receiving power converted by the voltage booster or the voltage reducer.
The voltage of a battery attached to the electric/electronic device is discharged as time lapses. Thus, if a charged voltage in the battery is discharged to a level below a predetermined voltage, the battery is placed in a charging unit for charging in order to normally operate the electric/electronic devices.
When the battery is charged by using the charging unit, the battery is usually charged in a state that it has not been completely discharged. Namely, before the battery is completely discharged, it is placed in the charging unit for charging thereof. As a result, even after charging is terminated, the battery fails to maintain a level above a predetermined voltage, which is called a memory effect. The reason is that if the battery mounted in the electric/electronic device is re-charged in such a state that it has been discharged to a level below a predetermined voltage, re-charging takes place at above a predetermined voltage, so the battery remembers only the voltage state.
In other words, an initially charged battery continuously provides a normal voltage to the electric/electronic device for a predetermined time, but if the battery has been charged and discharged by more than a certain number of times, it would not be fully charged even after charging due to the memory effect and ocan only be charged to below a predetermined voltage level. Consequently, since the battery fails to output a continuous voltage for a predetermined time, the electric/electronic device or equipment may not operate in an optimal manner.
Therefore, in order to minimize the memory effect of the battery, the battery should be completely discharged before re-charging, but usually, the battery is re-charged with a residual voltage not enough for the electric/electronic device to normally operate, so the memory effect inevitably causes the life span of the chargeable battery pack to decrease.
In order to reduce the memory effect of the battery pack, conventionally, the residual voltage is measured by the charging unit, and if the measured residual voltage is greater than a threshold value, the battery is forcibly discharged to drop the residual voltage to below the threshold value, and then, charging is started. There are several techniques and patents for such a charging device as described above, but no method for removing the memory effect by the memory pack itself has been proposed.
In addition, in the conventional art, in case that a battery pack includes a plurality of battery cells, the battery cells are connected in parallel, so all the battery cells are simultaneously charged and used up, resulting in a degradation of charging and discharging efficiency.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.